Electric Fields Flashcards

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1
Q

Define a field

A

A field is a region in which a body can experience a non-contact force.

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2
Q

What are the rules for drawing electric field lines?

A

When drawing electric fields:
The lines should never cross
The spacing of the lines represents the strength of the field
An arrow should be drawn to show the direction of force that a positive charge would feel

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3
Q

What is a field line (electric)?

A

The path a free positive test charge follows.

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4
Q

Describe a field between two oppositely charged plates

A

Field lines run parallel
At right angles to the plates
At the edges of the field the lines are slightly curved

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5
Q

What kind of a field is it between two oppositely charged plates?

A

Uniform field

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6
Q

Define electric field strength at a point in the field

A

The force per unit charge on a positive test charge placed at that point.

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7
Q

Electric field strength between plates is proportional to what?

A

Q/A
Q - charge
A - surface area

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8
Q

Define electric potential at a point in an electric field

A

Work done per unit positive charge on a positive test charge when it is moved from infinity to that point.

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9
Q

Define potential gradient (electric) at a point in an electric field

A

The change of potential per unit change of distance in a given direction.

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10
Q

How is potential gradient effected if the field is non-uniform?

A

Varies according to position and direction.

Closer equipotentials means greater potential gradient at right angles to them.

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11
Q

How is potential gradient effected if the field is uniform?

A

Equipotentials between the plates are equally spaced parallel to the plates.
Potential gradient is constant.

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12
Q

Define electric field strength

A

The negative of the potential gradient.

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13
Q

Define Coulombs law

A

The force of attraction or repulsion between two charges is proportional to the product of the masses and inversely proportional to the separation squared.

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14
Q

What is a point charge?

A

An expression for a charged object in a situation where distances under consideration are much greater than the size of the object.

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15
Q

If two forces are in the same direction, what is the resultant electric field strength formula?

A

E(1) + E(2)

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16
Q

If two forces are in opposing direction, what is the resultant electric field strength formula?

A

E(1) - E(2)

17
Q

If two forces are at right angles to each other, what is the resultant electric field strength formula?

A

Resolve using pythagorus.

sqrt(E(1)^2 + E(2) ^2)

18
Q

What can be found from a graph of force against separation?

A

Area = work done = Electrical potential energy

19
Q

What can be found from a graph of electric field strength against separation?

A

Area = Electrical potential

20
Q

What can be found from a graph of electric potential against separation?

A

Gradient = Electric field strength